Docs: The name of scroll ID attribute in the response is "_scroll_id" rather than "scroll_id"

Closes #10691

docs/reference/search/request/scroll.asciidoc

@@ -49,7 +49,7 @@ curl -XGET 'localhost:9200/twitter/tweet/_search?scroll=1m' -d '
 '
 --------------------------------------------------
 
-The result from the above request includes a `scroll_id`, which should
+The result from the above request includes a `_scroll_id`, which should
 be passed to the `scroll` API in order to retrieve the next batch of
 results.
 
@@ -84,7 +84,7 @@ curl -XGET 'localhost:9200/_search/scroll?scroll=1m' -d 'c2Nhbjs2OzM0NDg1ODpzRlB
 --------------------------------------------------
 
 IMPORTANT: The initial search request and each subsequent scroll request
-returns a new `scroll_id` -- only the most recent `scroll_id` should be
+returns a new `_scroll_id` -- only the most recent `_scroll_id` should be
 used.
 
 NOTE: If the request specifies aggregations, only the initial search response